Television apparatus



Au 28, 1934. H. M. DOWSETT ET AL 1,971,372

TELEVISION APPARATUS Filed May 4, 1932 2 Sheets-Sheet v l INVENTOR H.M. DOWSETT D- L. PLAIS TDWE fl ww ATTORNEY 1934. H. M. DOWSETT ET AL 1,971,372

TELEVI S ION APPARATUS Filed May 4, 1932 2 Sheets-Sheet 2 INVENTOR H.M. DOWSETT DL. PLAISTOWE ATTORNEY Patented Aug. 28, 1934 'rsmivision APPARATUS Harry Melville Dowsett, Winchmore Hill, London, and Donald Leopold Plaistowe, Leigh-ontlie-SeaEngland, assignors to Radio Corporation of America, a corporation of Delaware Application May 4, 1932, Serial No. 609,056 r In Great Britain May 20, 1931 2 Claims.

This inventionrelates to television apparatus. In televising a picture or scene it may sometimes be preferable to scan the scene of which an image is to be transmitted horizontally, that is,

- with lines running horizontally with respect to the scene, or vertically, that'is, with lines running vertically with respect to the scene, according to the nature or type of scene being scanned.

The present invention has for its principal object that of providingtelevision apparatus whereby horizontal or vertical scanning may be accomplished: at will, and wherein the change from one type of scanning to the other may be easily and quicklyproduced.

A further object of the invention is to provide improved television apparatus in which the ac curacy of the television signals being sent out from the transmitter may be checked during transmission so as to facilitate monitoring.

A still iurther object of the inyention is to provide that the essential requirements for transmitter scanning do not impose limitations onthe quality of the receiver scanning as employed in the monitoring arrangement.

Accordingto-this invention, atelevision transmitter comprises a Nipkow disc, means for projecting light over an area of the disc corresponding to the picture or-scene area, and a means for causing relative movement between the projecting apparatus. and the disc whereby the area may be moved to dif ferent parts of thedisc and the direction of scanningxaccomplished by the disc thereby changed. 7 j

Preferably the. disc comprises two spirals of apertures arranged one inside the" other. So arranged, one spiral may be used for transmission purposes and the other can then serve for monitoring i l The. appertures or the transmitter. spiral, the qmean spiral radius and the scanning area covered by this spiral on the disc may be smaller than in the receiver spiral.

It is then possible to use a projection lens of small aperture and focus in connection with the transmitter spiral such that the subject may be placed at that distance from the photo cells which enables the latter to be excited by a low power light source; while the apertures of the receiver spiral are made sufficiently large to suit .;;the low intensity of the neon tubes.

The invention is illustrated in the accompanying drawings in which Figure 1 shows schematically a transmitter scanning mechanism in accordance with the present invention viewed from the operators side and with part of the dust case DC represented as though it were transparent, Figure 2 shows the mechanism with the dust cover removed and viewed from the television subjects side, while Figure 3 shows schematically a receiver.

Referring now to the drawings, and first to Figures 1 and 2, the television transmitter therein shown comprises a Nipkow disc 1 with itsusual constant speed driving motor 2. The motor and disc are mounted preferably as a unit upon a frame 3 which is slidably arranged to be moved along a ramp or platform 4: inclined at an angle of 45 to'the vertical. The bottom of the frame may be mounted to slide on or between guides on the platform and the sliding movement is arranged to be imparted thereto by means of a nut 5 carried upon or with the frame. The nut engages with a threaded rod 6 mounted in bearings beneath the inclined platform and arranged to be rotated by means of a hand wheel 7. Also mounted on the motor and disc structure. is a pair of projection. lenses 8 and 9. The lens system 8 is positioned to project light over a picture area whose center is on a horizontal diameter of the disc, and the other lens system 9 is arranged to project light over; a. picture area whose center is on a vertical dia y r meter of thedisc. Both projection lenses are, of course, arranged on the mean spiral radius of the transmitting or inner spiral of apertures IS.

Mounted upon the general framework of the machine is a transmitter projection system co mprising prisms, lenses, or other suitable devices located within the casing PG for projecting a light. beam from a source within the box 3 towards the desired picture area to be projected. upon the inner or transmitting spiral of aper-g tures IS. Mounted near the upper end of the ramp or platform i is a monitoring neon tube 10 contained within a screening box 11 in such manner that the tube axis is vertical. Mounted near the bottom of the ramp or platform is a second monitoring neon tube 12 also contained within a screening box 13 so that the second tube has its axis extend in a horizontal direction. The neon tubes 10 and 12 are associated with viewing lenses or other optical systems VS and HS and are so positioned that the outer or monitoring spiral OS serves as the scanning means for what may be termed a local or monitoring receiver, the tubes being alternatively energized by electrical impulses obtained from the transmitting photoelectric cell or cells (not shown) which are connected in any suitable manner with transmitting equipment of desired for monitoring purposes.

12F and 12S while when it is in its top position the circuit to the tube 10 is completed through plugs and sockets 10.1 and 10S.

It will be seen that with this arrangement vertical and horizontal scanning may be ac complished at will, merely by rotating the hand wheel, so as to slide the frame carrying the disc and associated mechanism, into whichever of.

the two extreme positions is desired. In one of its extreme positions, the fixed projection mech anism will pass light through one of the projection lenses carried on the motor and disc assembly, while in the other. of the extreme positions light will be projected through the other of the projection lenses. It will also be appreciated that whether horizontal or vertical scanning be in use it is possible in either case to View the television image by means of the monitoring system provided before coupling the transmitter to line, or to whatever may be the communication channel. Since the transmitting and monitoring spirals are upon the same disc, there is no question of the provision of any special synchronizing mechanism as between the transmitter and the local receiver, provided For purposes of con venience in manufacture the two spirals may be mounted one upon a disc and the other upon an annulus embracing the disc, the disc and annulus being clamped together so as to form, in effect, a single disc. Alternatively, two separate discs may be provided, one for transmitting,

and one for monitoring, but so long as these discs are driven together, no difiiculties in synchronism will arise.

In an alternative arrangement, instead of providing two projection lenses mounted upon a movable motor and disc assembly, a single lens carried by or otherwise mounted in fixed relation to the projection apparatus, may be provided.

The receiver shown in Figure 3 comprises an ordinary single spiral Nipkow disc ND with which is associated two neon tubes NTV and NTH the former being utilized for receiving when vertical scanning is employed and the latter when horizontal scanning is employed.

. The neon tubes, either of which may be switched in as required by a switch SW, are viewed through view lens systems VLV and VLH. The apertures, the mean spiral radius and the scanning area of the receiver disc ND may all be larger than the corresponding dimensions for the transmitting spiral of apertures IS so that it is possible to use a projection lens of small aperture and focus in connection with the transmitter spiral such that the subject may be placed at that distance from the photo cells which enables the latter to be excited by a low power light source; while the apertures of the receiver spiral are made sufiiciently large to suit the low intensity of the neon tubes.

Having now described our invention, what we claim and desire to secure by Letters Patent is the following:

1. A television transmitter comprising a Nipkow disc provided with a plurality of independent spirals of scanning elements arranged one inside the other, means for causing a relative movement between the projecting apparatus and the disc so that the light projecting area of the disc corresponding to the picture or scene area may be moved to diiferent parts of the disc so as thereby to change the direction of the scanning lines, a frame for supporting the disc, a guide member for supporting the frame, and means for moving the disc upon the frame to opposite ends so that in one position the scanning elements of the disc trace an area formed from a succession of horizontal elemental strips and in the other position the scanning elements trace an area formed in a succession of vertical strips.

'2. Television apparatus comprising a scanning disc having two spirals of scanning elements one inside the other, a motor for driving the scanning disc, a frame member for supporting the motor and disc as a unit, a carrier member arranged at an angle of substantially 45 degrees, means for carrying the frame slidably upon the carrier, means to move the frame slidably up and down the carrier between extreme positions, a source of illumination having the effective center thereof opposite the end of the vertical radius to the mean circle of the outer spiral of scanning elements when the scanning disc is in one-of its extreme positions, a second source of illumination having its effective center at the end of the horizontal radius to the mean circle of the outer spiral of scanning elements when the scanning disc is in its other extreme limiting position, a plurality of stop members upon the carrier for determining the extreme positions of the scanning disc, means for energizing either of the light sources at will in dependence upon received television signals, and means for viewing either of said lamps at will so as to observe any picture built up thereon.

HARRY MELVILLE DOWSETT. DONALD LEOPOLD PLAISTOWE. 

